As a rolling bearing to be used in a highly corrosive environment, there are proposed a rolling bearing in which very expensive ceramics or stainless steel is utilized for an inner ring, an outer ring, and rolling elements and in addition a rolling bearing in which an antirust technique of providing an outer part with a specific sealing construction is adopted. For example, a corrosion-resistant rolling bearing in which the inner ring, the outer ring, and the rolling elements are made of ceramics is proposed (see patent document 1). There is also proposed a rolling bearing in which the inner ring and the outer ring are made of stainless steel and the surfaces thereof are subjected to surface treatment such as film treatment performed by Ni plating, Cr plating or phosphate (see patent documents 2 and 3). There is also proposed a bearing, an outer portion of which is provided with a seal consisting of a magnetic fluid which prevents the penetration of a corrosive gas thereinto (see patent document 4).